An optical endpoint system controls the overetching of a semiconductor device by using double optical endpoint detection. With a complex spacer, the system monitors the chemistry change at both the top TEOS/nitride interface and the bottom nitride/TEOS interface. This double optical endpoint method reduces the possibility of overetching the layers regardless of the variations in the thickness of the incoming film or the etching characteristics of the etch chamber.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of forming a semiconductor device on a semiconductor material of a first conductivity type, the method comprising the steps of: forming a first layer of material on the semiconductor material; forming a second layer of material on the first layer of material; forming a third layer of material on the second layer of material; etching the third layer of material until a first wavelength of light changes from a first intensity to a second intensity; and etching the second layer of material until a second wavelength of light changes from a third intensity to a fourth intensity.
2. The method of claim 1 wherein the third layer of material is etched in an etching chamber that has an etching chemistry, the etching chemistry being set to etch the third layer of material, and wherein the second layer of material is etched in the etching chamber, and the etching chemistry is changed to etch the second layer of material in response to the first wavelength of light changing from the first intensity to the second intensity.
3. The method of claim 1 wherein the first wavelength and the second wavelength are equal.
4. The method of claim 3 wherein the first intensity is less than the second intensity.
5. The method of claim 4 wherein the third intensity is greater than the fourth intensity.
6. The method of claim 3 the first intensity is greater than the second intensity.
7. The method of claim 6 wherein the third intensity is less than the fourth intensity.
8. The method of claim 1 wherein the first wavelength and the second wavelength are unequal.
9. The method of claim 8 wherein the first intensity is less than the second intensity.
10. The method of claim 9 wherein the third intensity is greater than the fourth intensity.
11. The method of claim 8 wherein the first intensity is greater than the second intensity.
12. The method of claim 11 wherein the third intensity is less than the fourth intensity.
13. A method of forming a semiconductor device on a wafer, the wafer having a semiconductor material of a first conductivity type, a layer of gate oxide formed on semiconductor material, and a gate formed on the layer of gate oxide, the method comprising the steps of: forming a first layer of material on the layer of gate oxide and the gate; forming a second layer of material on the first layer of material; forming a third layer of material on the second layer of material; etching the third layer of material until a first wavelength of light changes from a first intensity to a second intensity; etching the second layer of material until a second wavelength of light changes from a third intensity to a fourth intensity to form a side wall spacer that adjoins the gate; and implanting a dopant to form source and drain regions in the semiconductor material and dope the gate, the side wall spacer protecting a region of semiconductor material underlying the side wall spacer from the dopant.
14. The method of claim 13 wherein the third layer of material is etched in an etching chamber that has etching conditions, the etching conditions being set to etch the third layer of material, and wherein the second layer of material is etched in the etching chamber, and the etching conditions are changed to etch the second layer of material in response to the first wavelength of light changing from the first intensity to the second intensity.
15. The method of claim 13 wherein the first wavelength and the second wavelength are equal.
16. The method of claim 15 wherein the first intensity is less than the second intensity.
17. The method of claim 16 wherein the third intensity is greater than the fourth intensity.
18. The method of claim 15 the first intensity is greater than the second intensity.
19. The method of claim 18 wherein the third intensity is less than the fourth intensity.
20. The method of claim 13 wherein the first wavelength and the second wavelength are unequal.
21. The method of claim 20 wherein the first intensity is less than the second intensity.
22. The method of claim 21 wherein the third intensity is greater than the fourth intensity.
23. The method of claim 20 wherein the first intensity is greater than the second intensity.
24. The method of claim 23 wherein the third intensity is less than the fourth intensity.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
May 31, 2001
April 23, 2002
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